<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        body{
            width: 3000px;
            height: 3000px;
        }
    </style>
</head>
<body>
    <script>
        /*
        
        bom级别
            window.innerWidth
            window.innerHeight
            包含滚动条在内的尺寸  

        dom级别 
            document.documentElement.clientWidth
            document.documentElement.clientHeight

            其实拿到的是html 元素的尺寸  

            内容+内边距 不含边框  不含  滚动条 
        */


        console.log('bom级别宽度',window.innerWidth);
        console.log('bom级别高度',window.innerHeight);
        

        console.log('dom级别宽度',document.documentElement.clientWidth);
        console.log('dom级别高度',document.documentElement.clientHeight);

    </script>
</body>
</html>